Sen. John McCain Sunday warned failure to stop Russian President Vladimir Putin's "invasion" of Ukraine now will just encourage him to be more aggressive in Eastern Europe. McCain (R-Ariz.) said on CBS' "Face the Nation" Crimea was just a first step and "Moldova and the Baltics" could be next.

"It's a conflict that requires our participation, not through American ground troops, but our participation, our help, and our leadership and that is what seems to be missing," McCain said. The remarks came after Putin Sunday proposed statehood for eastern Ukraine and pro-Russian separatists attacked a Ukrainian military vessel.

McCain said the United States should help arm Ukraine and he doubts sending arms will make the situation worse.

"For God's sake, can't we help these people defend themselves? This is not an incursion, this is an invasion," McCain said.

"Give them the weapons they need, give them the wherewithal they need, give them the ability to fight. They will fight. And as far as Vladimir Putin is concerned, put strong sanctions (in place.) If you're looking at it from Vladimir Putin's viewpoint, ... he's doing pretty well with a minimum of penalty and as long as the Europeans are on his energy supplies, they're not going to do much."

Rep. Peter King (R-N.Y.) agreed, saying Putin has to realize there's "a price to pay" for his actions.

"He has to be told he cannot recreate a Soviet or Russian empire, and if we can provide weapons, and we should to the Ukrainians, I think we should do it at the earliest possible moment," King said.

Retired Gen. Anthony Zinni told NBC's "Meet the Press" Putin is testing U.S. leadership and "European will, resolve and cohesion." Zinni said it is necessary to engage Putin.

"We're going to need a way to walk this down where there's face-saving or else we're going to have a confrontation that we don't want.